Coupling of nucleic acids is one of the basic techniques in the field of molecular biology. The coupling of nucleic acids is used, for example, for introduction of a gene or detection of a base sequence, in combination with hybridization. For such a reason, coupling of nucleic acids is a very important technique used not only for basic studies in molecular biology but also for diagnosis or therapeutics in medical field, development or production of an agent for therapeutics or an agent for diagnosis, and development or production of an enzyme or a microorganism in the field of engineering and agriculture, for example.
In the related art, coupling of nucleic acids has been carried out by using, for example, a DNA ligase, etc. However, it is disadvantageous in that, for such reaction based on an enzymatic reaction occurring in a living body, a specific condition is required and the enzymes used are relatively expensive and not stable enough, etc. To overcome these disadvantages, a technology of coupling nucleic acids without using enzymes has been studied.
As a technology of coupling nucleic acids without using enzymes, there is a method using an organic compound reactive to a nucleic acid. In recent years, a technique of coupling nucleic acids based on photoreaction has been drawing attention due to the advantages that temporal and spatial control of the reaction is freely achievable and the reaction can be carried out under a mild condition compared to general organic chemistry, etc.
As for such a technique for photocoupling, a photocoupling technique using 5-cyanovinyldeoxyuridine and its derivatives (photocoupling nucleic acids or photoresponsive nucleic acids) is known (Patent Document 1: Japanese Patent No. 3753938 and Patent Document 2: Japanese Patent No. 3753942).
Although these photoresponsive nucleic acids have excellent characteristics, their synthesis is not easy, a long reaction time like several hours to several days is required to obtain a target compound in sufficient amount. In addition, as it is accompanied by a side reaction, yield is not high, i.e., it is only 50% to 60%.
Patent Document 1: Japanese Patent No. 3753938
Patent Document 2: Japanese Patent No. 3753942